Ecosystem carbon density and allocation across a chronosequence of longleaf pine forests

Forests can partially offset greenhouse gas emissions and contribute to climate change mitigation, mainly through increases in live biomass. We quantified carbon (C) density in 20 managed longleaf pine (Pinus palustris Mill.) forests ranging in age from five to 118 years located across the southeastern USA and estimated above and belowground C trajectories. Ecosystem C stock (all pools including soil C) and aboveground live tree C increased nonlinearly with stand age and the modeled asymptotic maxima were 168 Mg C/ha and 80 Mg C/ha, respectively. Accumulation of ecosystem C with stand age was driven mainly by increases in aboveground live tree C, which ranged from &lt;1 Mg C/ha to 74 Mg C/ha and comprised &lt;1% to 39% of ecosystem C. Live root C (sum of below-stump C, ground penetrating radar measurement of lateral root C, and live fine root C) increased with stand age and represented 4% to 22% of ecosystem C. Soil C was related to site index, but not to stand age, and comprised 39% to...森林可通过提升活生物量，部分抵消温室气体排放并助力气候变化减缓工作。本研究对分布于美国东南部的20个人工经营长叶松（Pinus palustris Mill.）林分开展了碳密度量化分析，这些林分的林龄跨度为5至118年，并估算了其地上与地下碳动态轨迹。包括土壤碳在内的所有碳库构成的生态系统碳储量，以及地上活立木碳储量均随林分年龄呈非线性增长，模型模拟得到的渐近最大值分别为168 Mg C/ha与80 Mg C/ha。生态系统碳储量随林分年龄的积累主要由地上活立木碳储量的增长驱动，后者的碳密度范围为<1 Mg C/ha至74 Mg C/ha，占生态系统总碳储量的比例为<1%至39%。活根碳（即伐桩下碳、探地雷达（ground penetrating radar）测量的侧根碳与活细根碳的总和）随林分年龄增长，占生态系统碳储量的4%至22%。土壤碳与立地指数相关，但与林分年龄无关，其占比为39%至……